A study for solving problems in a related art processing method that uses medication, filtering and so on is under progress in order to cope with environment destruction due to seawater taken into and discharged from the ballast tank of large-scale ships and ecosystem disturbance due to inflow of organisms to the foreign zone.
In case of most of large-scale ships including an oil tanker and a large-scale freighter currently in use, a ballast tank is provided to a lower portion of the ship in order to secure stability and a balance of the ship. The ballast tank is used in balancing the ship by taking in a predetermined amount of seawater in order to complement loss of balance of the ship in case there is no cargo in the ship.
At this point, an amount of the seawater taken in is set on the basis of a ship's size, namely, displacement. In case of a large-scale ship, frequently seawater more than ten thousand tons is taken in. In that case, marine microorganisms are contained in the taken-in seawater. In case a ship takes in seawater in a country or zone where the ship comes alongside a quay and then discharges the seawater in a foreign country or zone, the marine microorganisms taken in the seawater might propagate to the foreign zone.
The above-mentioned migration of the marine microorganisms does not nearly occur in the natural world but generates ecosystem disturbance such as a change in a representative species of living creatures and a red tide, thus causing very severe problems to the ecosystem.
To cope with these problems, methods for filtering the taken-in seawater with a filter or eliminating the marine microorganisms by inputting medicines into the taken-in seawater have been used to eliminate the microorganisms inside the ballast tank. In case of the method that uses the filter, and amount of the taken-in seawater is reduced, thus a problem in treating capacity. Further, since the mesh of a filter is limited, a complete treating of the microorganism is not performed.
Further, in case of inputting medicines, the marine microorganisms that come in can be eliminated but poisonous chemical material remaining inside the tank contaminates the neighboring zone when the seawater is discharged, whereby environment destruction is caused. Thus, currently, use of the medicines is regulated.